Physics of Curly Hair Structure

Physics of Curly Sheet Structure
Physics of Curly Sheet Structure - M. Gaines; APS/C. Cain; Igor/stock.adobe.com

Michelle Gaines has developed a classification system that can help customers find the best hair care products by looking at the mechanical and geometric properties of curly hair.

Having hair made up of tightly curled tresses, Michelle Gaines spends a lot of time thinking about how to manage curly hair. She claims she would have more time if she didn't have to spend so much time worrying about her and her daughter's hair. Now, she has taken it upon herself to gather physics-based information on which products may be most effective in the care of curly hair, by measuring the mechanical and geometric properties of curly hair. She works as an adjunct Professor of Chemistry at Spelman College. Her institution is a liberal arts college in Atlanta, historically for Black women.

Gaines first became interested in curly materials when she was a high school student and met a female materials scientist while attending a "take your daughter to work" event with her mechanical engineer father. At this point Gaines decided to use his study materials. After completing his PhD in chemical engineering, he worked as an intern at Cincinnati-based Procter & Gamble. Here he gained practical expertise by evaluating the mechanical properties of elastomers and other types of polymers. As a result of his research, he realized that combing and styling his own curly hair every day was comparable to a materials science experiment.

Gaines presented her approach to hair measurement and her concepts of how this could result in new and improved natural hair care at the American Chemical Society convention last month.

He spoke with Physics Magazine about his project.

Why are you researching hair?

My own hair often undergoes many different shape and appearance changes. My daily life is affected by it. Back in 1995, when my family worked in the corporate sector, black women like me had to straighten or braid their hair to fit in. However, there weren't many care products ready for our hair type. The common hair classification developed by L'Oréal included four types: straight, wavy, curly and mixed. However, the majority of available products were either wavy or straight. The “wavy” hair products that many Black women choose to use just didn't work to style our natural hair in an acceptable way.

Besides being a cultural issue, I've also found it to be a polymer-material issue as various hair types have different mechanical properties. In addition to better categorizing curly and tangled hair, more details were needed on personal care products that would work best with certain curl patterns.

What criteria did you use to classify the hair?

Numerous samples of various hair types were obtained by my students and partners and examined under the microscope. In order to relate the geometry of a hair strand to its mechanical properties and surface structure, we developed new geometric parameters to describe the hair strands. This gave rise to the stretch rate, a statistic that measures the amount of effort required to straighten a curled strand of hair. How many full waves, curls, or spirals, in other words, how many contours are in a given hair length, determines how this parameter is scaled.

Can a person evaluate this variable on their own?

Yes. Take a strand of hair and lay it on a ruler without stretching it. Then you can say “my hair fits this type and this shape” and give it a number by counting the number of repeating features in a given length. Our parameter largely fits into the qualitative framework established by the famous hairdresser Andre Walker. We hope to use this scale in the future to recommend product components based on a person's score on our scale after collecting additional data.

Is it difficult to choose the right product?

It's for curly hair types, as experts don't fully understand what moisture does to hair. The cuticle, which is a layer of fatty acids and keratin cells that overlap each other like roof tiles to protect the inner cortex of the hair, is located on top of each hair strand. When exposed to water, shampoo, and other substances, the cuticle layers open and close. My research team is studying how the cuticles of various hair types behave. We discovered that curly hair has lower porosity and significantly more closely spaced cuticle layers than their less curly cousins. As a result, hair with more frizz is more difficult to absorb water.

Does this have anything to do with hair keeping its curl on a sweltering day?

Yes. Curly hair cannot be straightened without water. But now it's our best friend as it defines the curl in its most natural state. Hair develops its natural curl when left to stay moist and dry on its own. This is a result of their ability to absorb moisture. When your curls are wrapped neatly, they are hydrated. However, if moisture seeps in, the hair swells and loses its natural curl, trying to seek water.

What does this mean for hair care?

While the difference in drying times between wavy and straight hair and curly and kinky hair is well known, the connection with porosity is a fascinating discovery. It may clarify why staying hydrated is essential to maintain natural hair.

If manufacturers want to create better hair products, they can use hydrogel polymers to regulate hydration. However, there is still much to learn about the natural state of hair, which includes both curly and wavy hair. We haven't created some links yet.

Source: physics.aps.org/articles/v1

Günceleme: 25/04/2023 00:08

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